Magnetic switch



Dec. 12, 1961 c. F. VANDEN BROECK 3,013,137

MAGNETIC SWITCH 2 Sheets-Sheet 1 Filed July 14, 1958 c. F. VANDEN BROECK3,013,137

Dec. 12, 1961 MAGNETIC SWITCH 2 Sheets-Sheet 2 Filed July 14, 1958 IN VEN TOR. CHM/fl E M? 4 0677 .8/105 C/f United States Patent 3,013,137MAGNETlC SWITCH Camiel F. Vanden Broeck, Tujunga, Califi, assignor, bymesne assignments, to Consolidated Electrodynamics Corporation,Pasadena, Calif., a corporation of California Filed July 14, 1958, Ser.No. 748,375 4 Claims. (Cl. 200-87) This invention relates to mechanicalswitches and more particularly to such switches which may bemechanically controlled.

In the field of switch devices it is desirable to obtain a switch whichcan be opened and closed at a high rate, yet with a minimum of contactnoise so that low lvel signals on the order of several microamps can beswitched. Where a large number of electrical devices are to beinterrogated at high speeds, it is customary in many instances to employa commutating switch of the type having a plurality of stationarycontacts and a moving arm. The various devices interrogated have anoutput signal connected to the various stationary contacts of thecommutating switch. The movable arm is rotated and engages thestationary contacts, thereby interrogating the various devices once eachrevolution. The wiping action of the moving contact as it crosses thestationary contacts presents several disadvantages, among which aresubstantially large electrical noise signals from the wiping action anda relatively short useful life from the frictional engagemnt of thewiping contact with the stationary contacts. As a consequence electricaloutput signals having an amplitude lower than that of the electricalcontact noise connot be detected. Because of the frictional wear andtear of the stationary and wiping contacts, the useful life of such acommutating switch is limited, and the necessity for periodic repair orreplacement renders such a switching device expensive to use as well asoften unreliable after only a few hours of use.

In order to overcome the foregoing disadvantages a switch is providedaccording to the present invention which is magnetically operated andcontrolled, and a plurality of them may be employed as a commutatingswitch which has no wiping contacts. High speed sampling of low levelsignals is permissible, and such switch arrangement is simple and easyto manufacture. Furthermore, it has a long useful life, is relativelysmall and is inexpensive to manufacture and maintain.

According to a preferred embodiment of this invention, any leaf-typeswitch may be employed provided the leaves are magnetizable. Numerousmagnetic relays commercially available may be suitable. An individualmagnet, such as a bar maget, is disposed adjacent to a leaf-type spring.The switch is preferably of the type which has an inherent bias force,normally holding the leaves open in the absence of a magnetic field. Thestrength of the bar magnet and its position relative to the leaf-typeswitch is such as to magnetize the leaves and close them against theinherent spring bias. A plurality of such switch assemblies are arrangedin a pattern, a circular pattern being preferred. With a circularpattern of such switches a circular member such as a disk may beemployed. The disk member is balanced to minimize mechanical vibrationsand includes an inner pole piece disposed toward the hub of the disk andan outer pole piece disposed about the periphery of the disk. Aplurality of magnets, such as bar magnets, are positioned between thetwo pole pieces with the north pole of each magnet associated with onepole piece and the south pole of each magnet associated with the otherpole piece. The magnets on the disk are positioned to lie in thevicinity of the magnets associated with the individual switchassemblies.

3,013,137 Patented Dec. 12, 1961 red In operation the magnet associatedwith the individual switch assemblies supplies a magnetic field to theleaf members of the switch which magnetizes and closes them against theinherent spring bias. The magnetic fields from the magnets in the diskare disposed in the vicinity of the leaf members and are poled tocounteract the magnetic fields of the magnets in the individual switchassemblies. Actually the two magnetic fields aid each other, but divertmagnetic lines of flux away from the leaf members. The effect then is tocreate a resultant magnetic field in the leaf members which isinsufficient to hold the leaf members closed against the inherent springforces, and accordingly the leaf members are separated by the inherentspring force. One portion of the disk is cut out. This cut-out portionhas no magnetic field and individual switch assemblies associatedtherewith are subjected only to the magnetic field of the magnet in theindividual switch assembly. Accordingly, the individual switchassemblies associated with the cut-out portion of the disk are closedwhile the remaining switches associated with the disk are opened. Thedisk is rotated, and the individual switches are sequentially closed fora short period and then opened as the cut-out portion of the disk passesthereabout. A plurality of switch assemblies may be provided on eachside of the disk, and a plurality of disks and associated switchassemblies may be provided in a compact arrangement.

Whenever moving magnets are employed in or near closed electricalcircuits, the problem of induced signals arises, and in order to secureaccurate measurements of electrical signals from switch devices underinterrogation, it is necessary to eliminate the effects of the inducedsignals. The problem associated with induced signals is overcome in thepresent invention by making the cut-out portion of the disk sufiicientlylarge, compatible with the speed at which the disk is driven, so thatthe individual switches closed by the stationary magnets associated witheach switch assembly can close the switch arms and remain free of anymoving magnetic field sutficiently long to interrogate electricaldevices associated therewith. The cut-out portion of the disk representsa field-free region, and in order to permit any transients which mightbe present to die out before an interrogation is made, the size of thecut-out portion may be increased as needed. Thus any transients whichmight be present are permitted to dissipate before minute electricalsignals from associated devices are sampled, and shortly thereafter theswitch may be opened. The time during which such a field-free region ispresent at a given switch is determined by the size of the cut-outportion and the speed of the movable disk. Such factors as polestrength, size of the cut-out portion and speed of the disk may bevaried to provide a given time period during which no signals areinduced in each of the closed switches and the associated electricalcircuits. It is during this period that the electrical devices underinterrogation are sampled and an accurate measurement made of theirelectrical output signals, substantially free and clear of any inducedsignal from the magnets in the moving disk which serve to open and closethe various circuits in a given order. Accurate electrical measurementscan be made with a commutating device of this type operated at highspeed.

These and other features of this invention may be more fully appreciatedwhen considered in the light of the following specification and drawingsin which:

FIG. 1 illustrates in cross section a commutating-type switch whichemploys no wiping contacts;

FIG. 2 is a cross-sectional view taken on the line 22 in FIG. 1 andillustrates a plurality of individual switch assemblies;

FIG. 3 illustrates in greater detail, partly in cross section, anindividual switch assembly;

FIG. 4 is a cross-sectional view taken on the line 4-4 of FIG. 3;

FIG. 5 is a view taken along the line 55 in FIG. 1, illustrating ingreater detail the disk assemblies in FIG. 1;

FIG. 6 is a cross-sectional view taken along the line 66 in FIG. 5.

Referring first to FIG. 1, a switch assembly according to the presentinvention is illustrated in cross section. It includes end plates 10 and12 disposed on opposite ends of a shaft 14. The shaft 14 is mounted inbearings 16 and 18 within respective end plates 10 and 12. Threerotatable disks 20, 21 and 22 are spaced along the shaft 14 by a pair ofinner spacers 24, 26 and a pair of outer spacers 28 and 30. A pluralityof spacers such as indicated at 32 are employed to properly position theouter periphery of the end plates 10 and 12, and a screw 34 is employedto pull the end plates together against the spacer 32. A plurality ofswitch assemblies 40 through 45 are disposed in a stationary position.As illustrated in FIG. 2, the switch assemblies extend around theperiphery of the disks 20 through 22. The switch assemblies 45 through51 of FIG. 2. are disposed on the right side of the disk 22 in FIG. 1. Asimilar arrangement of switches not shown in FIG. 2 are disposed on theleft side of the disk 22, but these latter switches include the switch44 seen in FIG. 2. The end plates 10 and 12 are each employed to supporta bank of switches. Inner switch support assemblies54 and 56 are used tosupport additional banks of switches on each side thereof.

Each switch includes a pair of terminals such as terminals 60 and 62 ofthe switch 45. Each switch is se- Cured to a circular insulation memberwithin the switch assembly. The switch 45 forinstance is friction fittedto an aperture in a circular insulation member 64 by a suitably shapedend portion 66.

Referring next to FIGS. 3 and 4, the details of the switch 45 in FIG. 1are illustrated, the remaining switches being identical in construction.The switch 45 includes a glass envelope 70 within which a pair of switcharms 72 and 74 are disposed. Switch contacts 76 and 78 are located onrespective flexible arms 72 and 74. These flexible arms are mechanicallybiased to a normally open position. The mechanical bias in the switcharms 72 and 74 is an inherent spring force which tends to part theseswitch arms, but separate springs may be used to urge the arms apart ifsuch is desired. A magnet 80 supplies a magnetic field to the flexiblearms 72 and 74 which normally holds them in the closed position againstthe spring bias. The glass envelope 70 and the magnet 80 are disposed ina suitable insulation material 82, and a metallic member 84 connects theterminal 62 to the metallic end 66 and the flexible arm 74.

Referring next to FIGS. 5 and 6, the details of the disk 22 areillustrated, the remaining disks 20 and 21 being of identicalconstruction. A hub 90 has a plurality of holes therein such asindicated at 92. These holes may be filled with a material such as leadin order to balance the disk assembly 22 and minimize mechanicalvibrations. Holes 94 are indicated with a filler material positionedtherein. A circular member 96 is attached to the hub 90 as by screws 98and forms an inner pole piece. A plurality of magnets 100 aredistributed about the periphery of the disk 22 in recesses formedtherein. A circular member 102 is connected as by screws 104 to theperiphery of the disk 22 and serves as an outer pole piece. A region 108of the disk 22 is removed as illustrated in FIG. 5. The magnets 100magnetize the inner pole piece 96 with one magnetic polarity and theouter pole piece 102 with the opposite magnetic polarity. As indicated,the pole pieces 96 and 102 are magnetized with a north and southpolarity respectively. The magnets 100 are uniformly distributed aboutthe disk 22 except in the vicinity of the cut-out portion 1%. Near thisportion the magnets are placed closer together to provide a strongermagnetic field which gives a fast snap action in opening and closing theswitch arms.

In operation the disk 22 in FIG. 1 is rotated by driving the shaft 14with suitable driving means not shown. As the disk 22 rotates past theswitches 45 through 51 of FIG. 2, the magnetic fields of the magnets 100com bine with the magnetic fields of the magnets positioned within theseindividual switch assemblies and divert or cancel the magnetic fieldthrough the switch arms. For example the magnetic field of the magnets100 reacts with the magnetic field of the magnet in FIG. 3 and reducesthe magnetic field in the switch arms 72 and 74 such that the magneticattraction established in the switch arms is less than the openingeffect of the inherent spring bias. The magnets may be placed about thesame distance radially from the center of the switch assembly as themagnet 80. It Was found, however, that a faster snap action is obtainedin the switch arms if the magnets are displaced slightly from oneanother in the radial direction. In either case these switch armsconsequently separate because of their inherent spring bias previouslymentioned. In essence the two magnetic fields are poled unlike, and theystarve or divert magnetic lines of flux from the switch blades disposedintermediate the two fields. As the cut-out portion 108 of the disk inFIG. 5 passes over the switches 45 through 51, the mag netic field fromthe magnets within the individual switches, such as 80 in FIG. 3, isunopposed and closes the switch or switches within the region 108. Inother words, the individual switch assemblies associated with the disk22 in FIG. 1 are opened by the opposing effect of the magnets 100 exceptfor those switches which are within the region of the cut-out portion108. The switches within this region are closed because the individualmagnet within each switch assembly is unopposed and closes the flexiblearms against their inherent spring bias. It is seen, therefore, that asthe disk 22 in FIG. 1 rotates,'the individual switches disposed oneither side are sequentially closed for a relatively short period,determined by the length of the gap 108, and then opened for arelatively long period.

Thus a novel switch device is provided which is very reliable inoperation, simple and easy to manufacture. The switch is Well adaptedfor use as'a commutating switch device. Since wiping contacts areeliminated, its useful life is extended and operating costs are reduced.It is to be understood that various modifications and numerous otherarrangements are readily suggested to one skilled in the art.

What is claimed is: r

1. A switching device including first means for providing a stationarymagnetic field, a pair of magnetizable switch arms spring biased tonormally occupy an open position, said switch arms being positionedwithin the magnetic field of said first means, the magnetic field ofsaid first means serving to close the switch arms against the springbias, a second means for providing a magnetic field to said switch armswhich opposes the magnetic field of said first means whereby the netmagnetic field applied to said pair of magnetizable switch arms isinsuflicient to magnetize the switch arms and cause them to close by amagnetic attraction against the spring bias, whereby the switch arms areseparated by the force of the spring bias, and third means forperiodically moving said second means to and from the vicinity of saidfirst means whereby the switch arms are periodically closed and opened.

2. A commutator switch device including a plurality of magnetic switcheseach having a pair of switch arms mechanically biased to one of twopositions, means to apply a first magnetic field to said switchessufficient in intensity to magnetize the switch arms and close themagainst the mechanical bias, said first magnetic field beingfixed inposition, means to apply a second magnetic field periodically to each ofthe magnetic switches, the means for applying a second magnetic fieldincluding a disk member having an inner pole piece and an outer polepiece disposed on said disk, a plurality of magnets disposed on the diskbetween said pole pieces for magnetizing the pole pieces with oppositepolarities, said disk having a cut-out portion with the magnetic fieldin the cutout portion being substantially zero, and means to retate themagnetic disk adjacent to the plurality of magnetic switches, wherebyall magnetic switches in the vicinity of the cut-out portion of thedis-k are closed by the fixed magnetic field and the remaining magneticswitches associated with said disk receive a net magnetic field from therotating disk and the fixed magnetic field which is insufficient toclose the switch arms of such switches against their mechanical biaswhereby they are opened.

3. The apparatus of claim 2 wherein the magnets arev spaced uniformlyaround the disk except near the cutout portion where the magnets aredisposed closer to gether to give a stronger magnetic field which inturn provides a fast snap action in opening and closing the switch arms.

4. A magnetic switch assembly including a plurality of switches eachhaving a pair of ma'gnetizable arms mechanically biased to the openposition, means for applying a fixed magnetic field to said switcheshaving sufficient intensity to magnetize the switch arms and close themagainst the mechanical bias, a magnetized disk having a cut-out portion,said magnetized disk being disposed adjacent said magnetic switches, andmeans to rotate said magnetized disk, the magnetic switches associatedwith the cut-out portion of said disk being operated to the closedposition by said fixed magnetic field, the magnetic switches associatedwith the remaining portion of said disk receiving a magnetic field whichcombines with the fixed magnetic field to provide a net magnetic fieldin the magnetizable arms insufficient to hold them closed against themechanical bias, whereby as the cutout portion of said magnetized diskapproaches each magnetic switch the switch is closed and remains closeduntil the cut-out portion of the magnetized disk recedes therefrom.

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